Periscopic viewing system

ABSTRACT

A periscopic rear view optical system for vehicles in which an image of a rearward objective is reflected downwardly from a rooftop mirror through a prismatic device constructed as a transparently faced housing filled with a liquid suitable for the optical path to be within the critical angle at the desired reflective faces for reflection of the image to the driver of the vehicle. A modification of the device includes adjustable prism faces to accommodate different driver heights, with the spatial dimension variations produced by the adjustment effecting a vertical movement of the device.

United States Patent 1191 Toy [ Oct. 28, 1975 PERISCOPIC VIEWING SYSTEM[76] Inventor: William A. Toy, 459 Henley Drive,

Bloomfield Hills, Mich. 48013 [22] Filed: Jan. 7, 1974 [21] Appl. No.:431,369

Related US. Application Data [62] Division of Ser. No. 215,498, Jan. 5,1972, Pat. No.

[52] US. Cl. 350/301; 350/302; 350/299 [51] Int. Cl. G02B 5/08 [58]Field of Search 350/288, 299, 303, 304,

[56] References Cited UNITED STATES PATENTS 3,058,395 10/1962 Mattsson350/302 3,456,999 7/1969 Hopp 350/52 3,659,927 5/1972 Moultrie 350/286Primary Examiner-Alfred E. Smith Assistant Examiner-Michael l TokarAttorney, Agent, or FirmGifford, Chandler & Sheridan [5 7] ABSTRACT Aperiscopic rear view optical system for vehicles in which an image of arearward objective is reflected downwardly from a rooftop mirror througha prismatic device constructed as a transparently faced housing filledwith a liquid suitable for the optical path to be within the criticalangle at the desired reflective faces for reflection of the image to thedriver of the vehicle. A modification of the device includes adjustableprism faces to accommodate different driver heights, with the spatialdimension variations produced by the adjustment effecting a verticalmovement of the device.

8 Claims, 3 Drawing Figures to observeir US. Patent 0m. 28', 1975 toobserver PERISCOPIC VIEWING SYSTEM RELATIONSHIP TO OTHER APPLICATIONSThis is a divisional application from my co-pending application Ser. No.215,498 filed Jan. 5, 1972 and now US. Pat. No. 3,754,288.

BACKGROUND OF THE INVENTION A. Field of the Invention My inventionrelates to optical systems, and more particularly to a periscopic rearview optical system for vehicles.

B. Description of the Prior Art Interior center mounted and exteriorside view mirrors, presently in use in automotive vehicles, presentvarious design problems and have inherent safety deficiencies and otherdisadvantages. A primary design limitation for such mirrors is therequirement that the straight-line path from the observer to the mirrorand from the mirror to the objective be unobstructed. Par tialobstruction in this path such as is caused by vehicle structure producesblind spots which are often hazard ous. Further, such mirrors themselvesobstruct the operators forward field of view and the reflected image inthe mirror may camouflage the forward blind spot and present a dangeroussituation, particularly with respect to pedestrians. Present mirrorsfurther provide only a relatively small view of the rearward scene,leaving blind spots on either side.

In early years of automobile manufacture when traffic was comparativelylight, body designs of vehicles using center mounted mirrors were talland box shaped. A mirror could be relatively large and be mounted in ahigh position to avoid many of the aforesaid problems. Newer vehicleshave been designed with lower roof lines in order to achieve lowercenters of gravity and smaller frontal areas, lowering the rear windowdimensions. The center mounted rear view mirror must thus be placed muchlower, which produces the deficiencies and disadvantages previouslydescribed. Enlarging the mirrors to cover a wider field of view isimpractical because obstruction of the forward view and the associateddanger would be increased. In addition, interior mirrors are inherentlydangerous in case of accident.

Attempts to overcome these problems have taken many forms. Convexmirrors, for example, have been tried, but these not only distort theimage but also produce unrealistic depth perception which itself isdangerous. Additional side view mirrors can further obstruct the forwardfield of view and require the operator to continuously shift his sightbetween two or more mirrors, distracting him from attention to the sceneahead. Side view mirrors of the size in use today provide essentiallymonocular viewing, and hence eliminate the necessary depth perception.Further, at night such side view mirrors reflecting lights from rearwardvehicles have a blinding effect. Other disadvantages of side viewmirrors are that they may be obstructed by vent window structure andbeing relatively low to the ground they are readily dirtied in wetweather by spray from vehicle wheels, as well as contributing to safetyhazard in case of an accident.

Recently, overhead periscopic mirrors have been recognized as providingthe most likely solution to these problems, but most proposed designspresent many problems of their own. For example, since a two mirrorsystem inverts the rear image, a third image correcting mirror must beintroduced. However, since the mirrors must be so located to prevent onefrom obstructing the line of sight of another, they need to be fairlywidely separated, hence lengthening the sight line and the associatedtunnel vision effect. If the mirrors are of moderate size, the operatorexperiences difficulty in keeping the image framed by the mirrors inline, while if the mirrors are made extremely large then innumerabledifficulties in vehicle construction, mirror mounting and the like areexperienced. In addition, large mirror costs may make them prohibitive.

High cost associated with prisms of reasonable quality and sufficientsize is also a problem with various resorts to prism systems.

In my co-pending application Ser. No. 128,498 filed Mar. 26, 1971 andnow US. Pat. No. 3,704,062 as a continuation of application Ser. No.779,922 filed Nov. 29, 1968, I proposed a solution to the variousproblems by introducing the concept of an intermediate beamsplittermirror, enabling the vehicle driver to look through it to a first mirrorfrom which the reflection of the rearward image downwardly by therooftop mirror is specularly reflected from the beam-splitter mirror.The mirrors may now be mounted in close juxtaposition to eliminate thetunnel vision problem and per mit relatively moderately sized mirrors toproduce an extremely wide angle field of view. However, the systemslight transmission is somewhat limited by the beam-splitter and variousghost images being reflected to the driver need to be masked.

Numerous rear view mirror and optical systems are described, and theirdeficiencies made apparent, in the Report PB186228 entitled MotorVehicle Rear Vision prepared for National Highway Safety Bureau, US.Department of Transportation, and published by the US. Department ofCommerce.

SUMMARY OF THE INVENTION Extensive study of rear view observationsystems, particularly relating to human engineering factors and to thepracticalities of modern vehicle design and manufacturing requirements,involving cost as well as other considerations, have led me to theconclusion that, in order to have the capability for achieving a highlight transmission rate, along with the various optical advantagesinherent in the system of my prior co-pending patent application, aprism type of system would seem to be the best from all standpoints.However, a study of prisms, as presently proposed for periscopicsystems, indicates that they have drawbacks in the fact that normalprisms are extremely expensive in the size needed, and for use byvehicle drivers who vary to a great degree in height they are limited asto adjustability. Therefore, the present invention proposes to use aprismatic system constructed as a transparent faced housing or housingsfilled with a liquid having an index of refraction suitable for theoptical path to be within the critical angle at the desired reflectivefaces. For example, plate glass, which has the optical flatness requiredin prism faces and is of relatively low cost, can be constructed to forma housing and be filled with a liquid such as sugar water. In order tokeep chromatic and spherical aberrations within acceptable limits, it isnecessary that the entrance and exit faces of the prism, or combinedprism faces, be maintained optically parallel at all times.Adjustability is now available by variably tilting two of the faces ofthe prism in such a manner that the optical parallelism is maintained.

As presently conceived, the housing is made in two sections, namely amain prism section and an optical wedge. The main prism section has anupper image receiving face, a sloped face which specularly reflects theimage forwardly to a back surface mirror face, which thence reflects theimage through the sloped face and through the adjacent optical wedgehaving a viewing face presented to the vehicle driver. The interior ofboth the main prism and the optical wedge are filled with the desiredliquid.

Such a prismatic system by itself serves the purpose of a rear viewperiscope and has the capability of a comparatively high lighttransmission rate, but it is desirable to incorporate adjustmentfeatures. This is readily accomplished in my invention by making two ofthe faces adjustable relative to the other faces. I have chosen to makethe viewing face of the optical wedge and the mirrored surface of themain prism adjustable by connecting them to the bodies of the housing byflexible bellows or rolling flexible seals. In order to maintain opticalparallelism of the viewing face of the optical wedge and the upperhorizontal image receiving face, it is necessary to adjust the mirroredface at onehalf the rate of the viewing face, which can be accomplishedthrough a simple mechanical or other preferred device. The mirroredface, alternately, could be carried interiorly and adjusted without theneed of special flexible seal.

An added dividend in the adjustable face feature is that in maintaininga constant total volume within the housings, instead of using aninterconnected separate expansible chamber, the main bodies of theprismatic structure are made to adjust vertically relative to the upperimage receiving face in maintaining a constant total interior volume.This adjustment automatically lowers the prismatic device for shorterdrivers and raises it for taller drivers. The image transmitted into thedevice through the upper horizontal receiving face is reflected from ahigher roof-mounted mirror sloped upwardly toward the rear of thevehicle. If desired, the upper mirror could be enclosed with a rearwarddirected receiving face, and the horizontal faces previously describedeliminated entirely so that the main prism housing would have an upperspecularly reflective face. In this case, the viewing face of theoptical wedge and the rearward face adjacent the upper reflective facewould have to be maintained optically parallel at all times. However, asa practical matter, the added weight of fluid is probably not worth theadvantage of eliminating the upper mirrored surface.

DESCRIPTION OF THE DRAWING For a more complete understanding of theinvention, reference may be had to the accompanying drawing illustratingpreferred embodiments of the invention, in which like referencecharacters refer to like parts throughout the several views and inwhich:

FIG. 1 is a vertical cross-sectional diagrammatic view of a simplifiedperiscopic system embodying the present invention;

FIG. 2 is a vertical cross-sectional diagrammatic view of anotherembodiment of the invention showing the system in one adjusted position;and

FIG. 3 is a vertical cross-sectional diagrammatic view of the system ofFIG. 2 illustrating it in a second adjusted position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates a vehicleroof 10 provided with an aperture 12 above which is disposed a rearsurface mirror 14 preferably carried by a support structure 16 (phantomline).

A prismatic structure 18, comprising a main prism housing 18a and anoptical wedge housing 18b secured together as a unit, is supportedwithin and depending from the aperture 12 as indicated.

The main prism housing 18a incorporates an upper preferably horizontaltransparent image receiving face 20 preferably mounted flush with theupper surface of the vehicle roof 10, a transparent prism face 22depending from closely adjacent the rear edge of the face 20 and slopingforward, and a forwardly disposed rear surface mirror face 24 dependingfrom housing structure 26, with its lower edge being disposed closelyadjacent the lower forward edge of the prism face 22.

The optical wedge housing 18b incorporates a forward sloped transparentprism face 28 parallel with and spaced slightly from the prism face 22of the main prism housing 18a, and a transparent viewing face 30depending from closely adjacent the upper rear edge of the prism face 28and diverging therefrom, the lower edges of the faces 28 and 30 beingsealed to a lower housing structure 32.

All of the faces 20, 22, 28 and 30 through which light will pass arepreferably of substantially the same index of refraction as is theliquid medium and will preferably be flat plate glass. The liquid withwhich the interior of the housings 18a and 18b are filled has thedesired index of refraction so that the appropriate critical angle ofthe interior light rays is achieved at the outer glass surface so intotal the housing and faces constitute ordinary prisms, but plate glassand the necessary liquid, which might be ordinary sugar water, are muchless costly than any solid prism, and have been found to perform verysatisfactorily. The expense of solid prisms arises from the fact thatthe glass or other material must be substantially flawless, and theprism faces must be ground and polished flat to a high degree ofaccuracy. Plate glass, on the other hand, is normally made flat with therequisite degree of accuracy, while the liquid has high lighttransmitting quality and can represent a flawless mass.

In operation, an image I from the objective viewed along the opticalaxis designated by the intermediate phantom line A is reflected firstfrom the upper mirror 14 downwardly through the image receiving face 20for refraction to the main prism face 22 at an angle which is greaterthan the critical angle y of the face 22 so that the image is totallyspecularly reflected, with no light transmission loss, forward to themirror face 24, from which the image reflects rearwardly to the prismface 22 at an angle 1 which is less than the critical angle y asindicated, so that it transmits through the face 22.

Since the faces 20 and 22 are not optically parallel, the light exitingthrough the face 22 would normally be diffracted. Therefore, the opticalwedge 18b is required, with the face 28 being parallel to the main prismface 22 and the face 30 being optically parallel with the main prismface 20 (Le, the optical axis A at in comparison to an optical axisreflecting between or-- dinary mirrors which would necessarily beseparated from each other to avoid the obstruction of one mirror byanother.

FIGS. 2 and 3 illustrate a modification incorporating the principlesdescribed in relation to. FIG. 1, but in which the optical axis isadjustable for accommodating different observer eye positions. As shown,a vehicle roof 40 is provided with an aperture 42 above which isdisposed a rear surface mirror 44 preferably carried by a supportstructure 46 optionally having a rear transparent window face 47. Aprismatic structure 48, comprising a main prism housing 48a and anoptical wedge housing 48b secured together as a unit, is supportedwithin and depending from the aperture 42 by means of a flexible bellowsor rolling flexible seal 50 peripherally secured at one end to an uppermain prism housing frame structure 52 and at the other end peripherallyto the inner surface of the aperture 42 as indicated.

The main prism housing 48a incorporates an upper preferably horizontaltransparent image receiving face 60 preferably mounted flush with theupper surface of the vehicle roof 40, a transparent prism face 62 havingits upper edge mounted to the upper rearward edge of the housing framestructure 52 and sloping downward and forwardly therefrom, and a rearsurface mirror 64 having its lower edge pivotally secured as at P to alower housing structure 63 closely adjacent the lower edge of the prismface 62 and its upper and side edges secured to one end of a flexiblebellows or rolling flexible seal 66 whose other end is secured to alower flange portion of the housing frame structure 52.

The optical wedge housing 48b incorporates a transparent prism face 68having its upper edge secured to a rear edge of the structure 52 and itslower edge secured to the forward side of the housing structure 63 to bedisposed closely adjacent and parallel to the main prism face 62 asshown, and a viewing face 70 having its upper edge pivotally secured asat P to the structure 52 closely adjacent the upper edge of the face 68and its lower and side edges secured to one end of a flexible bellows orrolling flexible seal 72 whose other end is secured to the rear side ofthe housing structure 63. The housings 48a and 48b are filled with anypreferred fluid having the desired index of refraction when the index ofrefraction of transparent faces 60, 62, 68 and 70 are considered and areopenly connected through any means such as a passage 74 so that, onadjustment as will be explained hereafter, the liquid may flow betweenthe housings as their volumes respectively change.

The mirror face 64 is angularly adjustable relative to the face 62 ofthe main prism housing to vary the optical axis A through the device aswill be seen on com- 1 the image receiving face 60 as the optical axischanges. These adjustments are possible due to the provision of theflexible seals 66 and 72 which provide a flexible sealing joint betweenthe respective faces and the housing structure.

In the present device as disclosed, adjustment of the viewing face mustbe at twice the rate of adjustment of the mirror face 64 in order tomaintain the necessary optical parallelism of the receiving and viewingfaces 60 and 70, and this is achieved by any desired mechanism such asthe linkage system shown, which comprises a link member 82 pivotallyconnected at one end as at 84 to the lower edge of the viewing face 70and at the other end as at 86 to a lower end of a lever 88 in turnpivotally fulcrummed as at 90 on a bracket 92 or the like supported bythe main prism housing 48a.

The other end of the lever 88 is pivotally secured as at 94 to the outerside of the mirror face 64. The link member 82 is preferably providedwith a toothed rack 82a engaged with a spur gear 96 rotatable by asuitable knob 98. As can be seen, rotation of the knob 98 actuates thelink member 82 to directly angularly adjust the viewing face 70 and toadjust the mirror face 64 through the lever 88 in the desired ratios.

As the spatial dimensions of the housings 48a and 48b change from theposition of FIG. 2 to the position of FIG. 3, varying their respectivevolumes, liquid will flow from the housing 48b through the passage 74into the housing 48a. This causes the entire prismatic structure 48 tomove downwardly relative to the upper image receiving face 60 tocompensate for the inward movements of the faces 64 and 70 and maintainthe total volume within the housings constant. This lowering of thestructure 48 from the position of FIG. 2 to that of FIG. 3 tends to movethe viewing face 70 to a more convenient height for shorter drivers, andthe reverse motion upwardly from the position of FIG. 3 to the positionof FIG. 2 tends to keep the device from obstructing forward vision of ataller observer.

Although I have preferred to vary the angular relationships of theviewing face and the mirror face 64 relative to the other faces of theprismatic sttucture 48, any two of the faces could be adjusted toachieve the same result, so long as the faces 68 and 62 remainessentially parallel to each other and the faces 60 and 70 remainoptically parallel at all times.

Also, the forward side of the housing frame 52 could extend downwardlyall the way to form a solid wall of the main prism housing 48a, with themirror face 64 being carried inside between such forward wall and theface 62, being adjusted in substantially the same fashion as shown inFIGS. 2 and 3 but entirely inside of the liquid filled structure, thuseliminating the need for the flexible seal 66.

Further, the upper rear window 47 could become a prismatic imagereceiving face, with the face 60 shown in FIGS. 2 and 3 beingeliminated, the liquid then filling the entire volume above the roofline. Also, in such a case, the mirror face 44 could be a flat glassplate or other transparent member forming a prism face at an angle suchthat the optical axis will be directed to it at greater than thecritical angle for specular downward deflection. It will be noted alsothat in such a case the faces 47 and 70 would have to be maintainedoptically parallel, i.e., the refraction encountered by a light ray at47 would be compensated for at 70 as with the faces 60 and 70 in FIGS. 2and 3. The structure of FIG. 1

could similarly be modified to add a rear window and remove the upperface 20. However, as a practical matter, the added weight of liquid inthe upper space above the roof line might not compensate for theincreased transmission capabilities and other advantages of such amodification.

For reasons of automotive styling when air drag is considered and forcost considerations, it is important to keep the size of the externalparts as small as possible. An additional feature of the invention isthe fact that light rays upon entering the prism medium bend toward thenormal, which has an effect similar to further shortening of the opticalpath and makes it possible to use a smaller top mirror in attaining agiven field of view under constant conditions.

Although I have described and shown only a few possible embodiments ofthe invention, it will be apparent to one skilled in the art to whichthe invention pertains that various other changes and modifications maybe made therein without departing from the spirit of the invention orthe scope of the appended claims.

I claim:

1. In a periscopic viewing apparatus a prismatic structure having animage receiving face,

interiorly reflective faces, and a viewing face, the image receivedthrough said receiving face being transmitted to said reflecting facesand thence outwardly through said viewing face,

said prismatic structure further comprising a housing and an opticalwedge, said interiorly reflective faces being a part of said housing andsaid viewing face being a part of said optical wedge,

said housing having a chamber containing light transmitting liquidhaving the necessary index of refraction when combined with said facesto effect prismatic performance of said structure.

2. The apparatus as defined in claim 1 and wherein said wedge comprisesa housing having a chamber, said chamber being defined in part by saidviewing face, said housing including a light transmitting face disposedadjacent one of the reflective faces of said first mentioned housing,said chamber being filled with a light transmitting liquid having thenecessary index of refraction when combined with said wedge faces toeffect prismatic performance of said wedge.

3. The apparatus as defined in claim 1 and in which said faces compriseplate glass and said liquid comprises sugar water.

4. The apparatus of claim 1 wherein said faces are all planar.

5. The apparatus of claim 1 wherein said faces comprise plate glass.

6. The apparatus of claim 1 wherein at least some of said faces compriseplanar light transmitting elements.

7. The apparatus of claim 1 and including means permitting at least twoof said faces to be adjustable angularly with respect to other faces.

8. The apparatus of claim 1 and including means permitting some of saidfaces to be vertically movable relative to another face.

1. In a periscopic viewing apparatus a prismatic structure having animage receiving face, interiorly reflective faces, and a viewing face,the image received through said receiving face being transmitted to saidreflecting faces and thence outwardly through said viewing face, saidprismatic structure further comprising a housing and an optical wedge,said interiorly reflective faces being a part of said housing and saidviewing face being a part of said optical wedge, said housing having achamber containing light transmitting liquid having the necessary indexof refraction when combined with said faces to effect prismaticperformance of said structure.
 2. The apparatus as defined in claim 1and wherein said wedge comprises a housing having a chamber, saidchamber being defined in part by said viewing face, said housingincluding a light transmitting face disposed adjacent one of thereflective faces of said first mentioned housing, said chamber beingfilled with a light transmitting liquid having the necessary index ofrefraction when comBined with said wedge faces to effect prismaticperformance of said wedge.
 3. The apparatus as defined in claim 1 and inwhich said faces comprise plate glass and said liquid comprises sugarwater.
 4. The apparatus of claim 1 wherein said faces are all planar. 5.The apparatus of claim 1 wherein said faces comprise plate glass.
 6. Theapparatus of claim 1 wherein at least some of said faces comprise planarlight transmitting elements.
 7. The apparatus of claim 1 and includingmeans permitting at least two of said faces to be adjustable angularlywith respect to other faces.
 8. The apparatus of claim 1 and includingmeans permitting some of said faces to be vertically movable relative toanother face.